In lumber mills it is often necessary to trim pieces of lumber. For example, some boards may have defects at their ends. It is desirable to trim the boards to cut off the defects. There exist various control systems for determining where a board should be cut to remove defects while optimizing the value of the board. Such systems can be connected to a lumber positioning system upstream from a trim saw. The lumber positioning system positions each board at a longitudinal position determined by the control system so that the trim saw will cut the board at one or more desired locations.
Examples of lumber positioning systems are described in the following patents:
U.S. Pat. No. 6,311,828 (Newnes et al.)
U.S. Pat. No. 6,651,798 (Newnes et al.)
U.S. Pat. No. 6,705,190 (Newnes et al.)
U.S. Pat. No. 6,173,829 (Jackson et al.)
U.S. Pat. No. 5,865,080 (Jackson)
U.S. Pat. No. 5,911,302 (Jackson)
U.S. Pat. No. 6,173,829 (Jackson et al.)
U.S. Pat. No. 6,382,067 (Gagnon)
By and large, existing lumber positioning systems include some mechanism for moving lumber coupled control mechanisms that react in real time to stop the lumber from moving from the desired position.
It is generally desirable to operate lumber mills at higher speeds than have been prevalent in the past. Current mechanisms have reached the limit where higher speeds are not practical due to the response times of mechanical components and the limitations imposed by physics on the designs. At high speeds the times taken for actuators to move to positions dictated by control systems become significant. This limits the rate at which such mechanisms can operate.
There is a need for alternatives to existing lumber positioning systems. There is a particular need for cost-effective systems for positioning lumber and similar objects that can operate accurately while the objects are being moved quickly.